GLP-2 as an indicator and modulator of acute inflammation improves cardiac function and survival in sepsis

Purpose

GLP-1 and GLP-2 (glucagon-like peptide-1/2) are gut hormones secreted in response to food. While GLP-1 controls glucose metabolism, GLP-2 is a local gut growth factor regulating intestinal nutrient absorption. GLP-2 has been found to be upregulated in patients with colitis. We hypothesize that beyond its local intestinal function GLP-2 might be involved in systemic immune responses.

Methods and results

To analyze whether GLP-2 secretion is modulated by the immune system, we measured circulating GLP-2 levels in 2 clinical cohorts. In the first cohort (n=34) GLP-2 levels increased over time following cardiac surgery as an inflammatory stimulus. In the second cohort 223 patients with sepsis had a 3.9 fold increase of GLP-2 plasma levels vs. 53 healthy controls (3.0 ng/mL vs. 11.4 ng/mL; p<0.001). High GLP-2 levels were associated with markers of inflammation (IL-6, PCT, CRP), septic cardiomyopathy (NT-proBNP) and independently predicted mortality in humans with sepsis. Induction of sepsis in mice by endotoxin or cecal ligation puncture strongly increased GLP-2 levels independent from food intake. By injecting various proinflammatory cytokines and inducing sepsis in IL1R−/− and IL6−/− mice we identified that inflammation upregulates GLP-2 secretion through IL-6. To identify the source of GLP-2 secretion under inflammation, we induced sepsis in Gcg−/− mice lacking endogenous GLP-2 production with a tissue-specific reactivation of Gcg in gut L-cells (GcgRAΔvilCre) or pancretic alpha cells (GcgRAΔPDX1-Cre). We observed sepsis-induced GLP-2 secretion to be derived from the pancreas and not from the gut. Additional in-vitro and ex-vivo approaches revealed that IL-6 directly activates GLP-2 secretion from pancreatic alpha cells. Gcg−/− mice lacking GLP-2 production and Glp2r−/− mice show aggravated sepsis indicating that endogenous upregulation of GLP-2 is protective. Finally, we analyzed whether inflammatory upregulation of GLP-2 has immunomodulatory relevance. We administered GLP-2 or saline as control per central jugular vein catheter mice who underwent CLP. GLP-2 treatment improved LV-contractility (dp/dtmax) in septic cardiomyopathy (control 7361 vs. GLP-2 9500 mmHg/s; p<0.01), inhibited sepsis-induced hypotension and reduced mortality (p=0.018). Mechanistically GLP-2 reduced myeloid immune cell infiltration into heart and liver tissue and decreased proinflammatory cytokine levels in various organs and the blood (TNF-α, IL-6 and IL-1β). After broad GLP-2 receptor profiling we found maximum mRNA expression in gut tissues with no expression on immune cells. By further mechanistic studies we found GLP-2 to protect against sepsis-induced gut barrier dysfunction.

Conclusions

Here we identified a counter-regulatory control system in which IL-6 derived upregulation of GLP-2 secretion limits excessive innate immune responses and protects against sepsis. These findings might open new avenues for the treatment of patients with inflammatory diseases.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): European Foundation for the Study of Diabetes, European Research Area Network on Cardiovascular Diseases (ERA-CVD and BMBF), Deutsche Forschungsgemeinschaft (DFG)

Identification and Tissue-Specific Characterization of Novel SHOX-Regulated Genes in Zebrafish Highlights SOX Family Members Among Other Genes

SHOX deficiency causes a spectrum of clinical phenotypes related to skeletal dysplasia and short stature, including Léri-Weill dyschondrosteosis, Langer mesomelic dysplasia, Turner syndrome, and idiopathic short stature. SHOX controls chondrocyte proliferation and differentiation, bone maturation, and cellular growth arrest and apoptosis via transcriptional regulation of its direct target genes NPPB, FGFR3, and CTGF. However, our understanding of SHOX-related pathways is still incomplete. To elucidate the underlying molecular mechanisms and to better understand the broad phenotypic spectrum of SHOX deficiency, we aimed to identify novel SHOX targets. We analyzed differentially expressed genes in SHOX-overexpressing human fibroblasts (NHDF), and confirmed the known SHOX target genes NPPB and FGFR among the most strongly regulated genes, together with 143 novel candidates. Altogether, 23 genes were selected for further validation, first by whole-body characterization in developing shox-deficient zebrafish embryos, followed by tissue-specific expression analysis in three shox-expressing zebrafish tissues: head (including brain, pharyngeal arches, eye, and olfactory epithelium), heart, and pectoral fins. Most genes were physiologically relevant in the pectoral fins, while only few genes were also significantly regulated in head and heart tissue. Interestingly, multiple sox family members (sox5, sox6, sox8, and sox18) were significantly dysregulated in shox-deficient pectoral fins together with other genes (nppa, nppc, cdkn1a, cdkn1ca, cyp26b1, and cy26c1), highlighting an important role for these genes in shox-related growth disorders. Network-based analysis integrating data from the Ingenuity pathways revealed that most of these genes act in a common network. Our results provide novel insights into the genetic pathways and molecular events leading to the clinical manifestation of SHOX deficiency.

Functional Characterization of Rare Variants in the SHOX2 Gene Identified in Sinus Node Dysfunction and Atrial Fibrillation

Sinus node dysfunction (SND) and atrial fibrillation (AF) often coexist; however, the molecular mechanisms linking both conditions remain elusive. Mutations in the homeobox-containing SHOX2 gene have been recently associated with early-onset and familial AF. Shox2 is a key regulator of sinus node development, and its deficiency leads to bradycardia, as demonstrated in animal models. To provide an extended SHOX2 gene analysis in patients with distinct arrhythmias, we investigated SHOX2 as a susceptibility gene for SND and AF by screening 98 SND patients and 450 individuals with AF. The functional relevance of the novel mutations was investigated in vivo and in vitro, together with the previously reported p.H283Q variant. A heterozygous missense mutation (p.P33R) was identified in the SND cohort and four heterozygous variants (p.G77D, p.L129=, p.L130F, p.A293=) in the AF cohort. Overexpression of the pathogenic predicted mutations in zebrafish revealed pericardial edema for p.G77D and the positive control p.H283Q, whereas the p.P33R and p.A293= variants showed no effect. In addition, a dominant-negative effect with reduced heart rates was detected for p.G77D and p.H283Q. In vitro reporter assays demonstrated for both missense variants p.P33R and p.G77D significantly impaired transactivation activity, similar to the described p.H283Q variant. Also, a reduced Bmp4 target gene expression was revealed in zebrafish hearts upon overexpression of the p.P33R mutant. This study associates additional rare variants in the SHOX2 gene implicated in the susceptibility to distinct arrhythmias and allows frequency estimations in the AF cohort (3/990). We also demonstrate for the first time a genetic link between SND and AF involving SHOX2. Moreover, our data highlight the importance of functional investigations of rare variants.

Glucose-dependent insulinotropic peptide secretion is induced by inflammatory stimuli in an interleukin-1-dependent manner in mice

Recently, glucagon-like peptide-1 (GLP-1) levels have been found to be increased in response to inflammatory stimuli, leading to insulin secretion and prevention of hyperglycaemia during endotoxemia in mice. In the present study, we assess the relevance of the other incretin hormone, glucose-dependent insulinotropic peptide (GIP), as a regulator of glucose metabolism under inflammatory conditions. We found that lipopolysaccharide (LPS) increased GIP secretion in a time- and dose-dependent manner in C57BL/6J mice. To elucidate the underlying mechanisms, mice were injected with inflammatory cytokines known to be released by LPS. Circulating GIP levels significantly increased in response to interleukin (IL)-1β but not IL-6 or tumour necrosis factor (TNF)-α administration. Using respective knockout mice we found that LPS-mediated GIP secretion was selectively dependent on IL-1 signalling. To evaluate the functional relevance of inflammatory GIP secretion we pretreated mice with the GIP-receptor antagonist (Pro3)GIP. This blunted LPS-induced TNF-α and IL-6 secretion but did not affect LPS-induced insulin secretion or blood glucose-lowering. In conclusion, GIP provides a novel link between the immune system and the gut, with proinflammatory-immune modulatory function but minor glucose regulatory relevance in the context of acute endotoxemia.

Dendritic cells conditionally transformed by v-relER oncogene express lymphoid marker genes

The initiation of primary immune responses is the key function of specialized antigen presenting cells, the dendritic cells (DC). DC of myeloid origin capture antigens in tissues, migrate to lymphoid organs and stimulate T cell responses. A subset of DC has been described which expresses lymphoid determinants and has potential regulatory functions. Conditional transformation of chicken bone marrow progenitors with v-relER, a v-rel estrogen receptor (ER) fusion gene, allows expansion of progenitors that can be induced to differentiate into DC in vitro. In this paper we describe that v-relER cells exhibit both myeloid and lymphoid surface markers, while B cell, T cell and NK (natural killer)-specific surface markers are absent. v-relER DC express, however, cytoplasmic CD3 protein and mRNA for CD8alpha and the lymphoid transcription factor GATA-3. These data suggest that v-relER DC might be related to the lymphoid subset of DC described in mammals.

Chronic angiotensin II antagonism with losartan in one-kidney, one clip hypertensive rats: effect on cardiac hypertrophy, urinary sodium and water excretion and the natriuretic system

OBJECTIVE

To evaluate the effect of 7-day angiotensin II antagonism with losartan, an AT1-receptor antagonist, on systolic blood pressure, renal sodium and water excretion and on the atrial natriuretic factor system in one-kidney, one clip hypertensive rats.

METHODS

The one-kidney, one clip hypertensive rats were separated into four groups: untreated (group 1), low-sodium diet (group 2), losartan (20 mg/kg orally, group 3) and low-sodium diet with losartan (group 4). All of the rats were kept in metabolic cages with urinary volume, urinary sodium level and water intake being evaluated daily. Body weight and blood pressure were assessed before treatment and at the end of the observation period. Renal glomerular and papillary atrial natriuretic factor receptors were assessed by radioligand binding experiments.

RESULTS

No differences were observed either in body weight or in blood pressure between groups at the outset After 1 week, blood pressure was 184+/-4, 184+/-7, 170+/-5 and 78+/-8 mmHg, in groups 1, 2, 3 and 4, respectively. Group 3 rats failed to gain weight and had high urinary volume. In contrast, group 4 rats lost 15% of their original body weight. Both of the losartan-treated groups presented an apparently reduced cardiac hypertrophy but it was only clear in the low-sodium diet group. Both of the losartan-treated groups had high plasma renin activity. All of the three treated groups showed upregulation of glomerular and no changes in papillary atrial natriuretic factor receptors. Overall, mortality was 18, 27, 0 and 36% in groups 1, 2, 3 and 4, respectively.

CONCLUSION

Losartan administration reduces blood pressure in one-kidney, one clip rats only when combined with a low-sodium diet. Both low-sodium diet and angiotensin II antagonism upregulate renal glomerular but not papillary atrial natriuretic factor receptors, suggesting a divergent regulatory mechanism.

Captopril treatment does not restore either the renal or the ANF release response during volume expansion in moderate to severe high output heart failure

OBJECTIVE

Atrial natriuretic factor (ANF) release and the renal response to moderate volume expansion have been shown to be conserved in rats with a mild to moderate degree of high output heart failure (aortocaval shunt). The aim of this study was to investigate whether these variables are also conserved in animals with moderate to severe heart failure induced by an aortocaval shunt. The effect of angiotensin converting enzyme (ACE) inhibition by captopril on these responses was also investigated.

METHODS

An aortocaval shunt was developed in Sprague-Dawley rats weighing 180-200 g; sham operated rats served as controls. Three weeks after surgery, three experimental groups were established: aortocaval shunt and sham operated controls, and aortocaval shunt rats treated with captopril during the last week before the experiments were started. Four weeks after surgery, haemodynamic variables, ANF release, diuresis, and natriuresis were evaluated following a moderate volume expansion.

RESULTS

Mean arterial blood pressure was lower in shunt animals and still lower in the ACE inhibited group than in the sham operated controls. Central venous pressure and left ventricular end diastolic pressure (LVEDP) were significantly higher in untreated shunt rats than in their controls. ACE inhibition returned the raised central venous pressure, but not LVEDP, to control values. Shunt rats had lower baseline urinary sodium excretion (UNaV), urinary volume, and packed cell volume than their sham operated controls. ACE inhibition reversed baseline urinary volume to control values. Baseline COOH terminal and HN2 terminal ANF were greatly increased in both treated and untreated shunt rats. Volume expansion was performed three times in conscious animals at 15 min intervals with human plasma protein fraction. Its effect on LVEDP was similar in all three groups, but the increase in central venous pressure was much higher in untreated shunt animals. UNaV, urinary volume, and the release of COOH terminal and NH2 terminal ANF in response to volume expansion were blunted in both treated and untreated shunt rats when compared with their sham operated counterparts. Both absolute and relative heart weights were significantly lower in captopril treated shunt animals than in the untreated shunt group, the latter presenting very significant cardiac hypertrophy.

CONCLUSIONS

Aortocaval shunt animals with moderate to severe heart failure show a blunted ANF release and renal response to volume expansion, which, despite significant haemodynamic improvement, are not restored by ACE inhibition.

[Arterial complications of arthroscopic meniscectomies. Apropos of three cases]

The authors report three exceptional cases of vascular lesions occurring during arthroscopic meniscectomies involving the posterior horn of the lateral meniscus. These lesions consisted of false aneurysms of the popliteal artery detected early (1 month) or later (5 months and 3 years) after the procedure, one of which formed a fistula with the accompanying vein. This later case resulted in intermittent claudication of the calf and the other two cases presented with painful flexion deformity of the knee. In the case diagnosed after 1 month, the false aneurysm arose from a punctate injury to the artery and was treated by direct arterial suture. In the other two cases, treatment consisted of excision of the false aneurysm and restoration of arterial continuity by an autologous saphenous vein graft. The quality of the clinical result was confirmed angiographically in all three cases. The anatomy predisposes to this complication which can be avoided by respecting a few simple precautions. The surgeon must be avoided by respecting a few simple precautions. The surgeon must be aware of and look for signs of this complication in order to allow early diagnosis.

IL-6 mRNA expression in CD25 positive malignant lymphomas

We recently demonstrated that IL-2 is produced by reactive T cells in CD25-positive malignant lymphomas (ML). Using in situ hybridization, we investigated IL-6 mRNA expression in these CD25-positive ML. The ML tested included 9 anaplastic large cell lymphomas and 3 B-diffuse large cell lymphomas. Five CD25-negative ML were studied as controls. We show that IL-6 producing cells are present in all these ML. The density of positive cells was heterogeneous from case to case. However 3 cases of CD25-positive ML showed a dramatically higher density of IL-6 producing cells (70, 50, 43 producing cells per 10,000 cells, respectively) as compared to the other 9 cases of CD25-positive ML (mean 6.03 +/- 2.1 per 10,000). Morphological and topographical data suggested that several types of cells including fibroblasts, lymphocytes, macrophages and endothelial cells may synthesize IL-6. A combination of immunohistochemistry and in situ hybridization showed that reactive T cells and endothelial cells express the IL-6 gene whereas CD30-positive ML cells do not express this gene. Previous studies showed that IL-6 was capable to induce IL-2 receptor expression as well as production of IL-2 and stimulation of lymphomatous cells growth. Our present results indicate that the paracrine production of this cytokine may play a role in the proliferation of malignant lymphomas.

Simple, rapid, and effective method of producing aortocaval shunts in the rat

STUDY OBJECTIVE - The aim of the study was to develop a new procedure to produce abdominal aortocaval shunts in the rat without vascular microsurgery. PROCEDURE - The inferior vena cava and abdominal aorta were exposed by laparotomy. The aorta was punctured caudal to the left renal artery with an 18 gauge disposable needle which was advanced into the vessel, perforating the adjacent wall between aorta and vena cava and penetrating the latter. A bulldog vascular clamp was placed across the aorta cephalic to the puncture, the needle was withdrawn, and the aortic puncture point was sealed with a drop of cyanoacrylate glue. The clamp was removed 30 s later. Patency of the shunt was verified visually by swelling of the vena cava and admixture of arterial and venous blood. No local haemorrhages were seen. The laporatomy was then closed. The procedure takes less than 10 min. RESULTS - Of 11 rats which received this procedure, only one died within 24 h. All the other animals were killed 4 weeks after operation. Nine of these 10 animals had developed cardiac hypertrophy of about the same magnitude. There were no changes in sham operated controls. CONCLUSIONS - This is a reproducible, simple and rapid method of developing high output heart failure and cardiac hypertrophy in the rat which could be useful in many laboratories.